(a) Field of the Invention
This invention generally relates to a system and method for supporting a valve stem of the type commonly used with valves used to deliver or exhaust gases from the combustion chamber of an internal combustion engine. More particularly, but not by way of limitation, to a valve guide insert and valve stem support components for a poppet type valve in an internal combustion engine.
(b) Discussion of Known Art
Many internal combustion engines, and particularly four stroke engines, use valves to control the ingress and egress of gases to used or produced in operation. These valves typically include a poppet valve section mounted on a stem which is used to move the valve between an open and a closed position. The stem typically rides in a valve guide which is made or cut from the same material as the balance of the head. The guide will include an aperture that has been machined to provide a smooth finish and which will accept the valve stem and allow lubrication and sliding motion of the stem within the guide. Since the head is typically made from a relatively mild material, the valve guide must be of a size that allows significant distribution of the loads imposed by the stem. This frequently requires that the valve guide and valve guide boss protrude into the runner or flow ducts provided by the head. The protrusion of the valve guide boss into the runner limits the effectiveness of the runner. The flow of gas that can be delivered by the runner is thus limited to the maximum amount deliverable through the constriction produced by the valve guide boss.
It is known that valve guide inserts may be incorporated into the head. The practice of using valve guide inserts is known, and particularly common in re-conditioning of heads with valve guides that have been significantly enlarged during service. Known designs for valve guide inserts such as the insert taught in British Patent No. 196,653 to A. J. Hawes Elverson which teaches the use of a threaded valve guide which attaches to the head by means of the threads. Another known valve guide is shown in British Patent No. 202,028 to C. Frederick Ryland, which again shows a threaded valve guide that is threadably connected directly to the head of the motor. Other known valve insert devices which include threaded portions include U.S. Pat. No. 908,604 to Odenkirchen. These inserts, however, do not provide a means for progressively tightening the fit of the guide in the head.
Yet another known valve guide insert is taught in British Patent No. 159,822 to E. Bougatti. The Bougatti invention includes a valve guide which is conical in shape and which includes a threaded portion that has been adapted to extend over the top surface of the head once installed. This valve guide is driven into the head where it is retained by the elastic deformation of the valve guide and the head. The threaded portion of the Bougatti valve guide serves for providing a surface which may be used to pull and extract the guide when necessary to do so.
Other known devices include French Patent No. 924,584 to the Austin Motor Company, Limited, and which teaches a two part valve guide, with one part being threadably attached to the runner side of the head.
It is known that it would be advantageous to provide a valve guide seal to control lubrication of the stem as it moves within the guide. Examples of these devices include U.S. Pat. No. 3,885,546 to Foley et al., and U.S. Pat. No. 4,124,220 to Leone et al.
Still other known valve guide designs reveal configurations with contours on the external surface of the valve guide. For example, the configuration of the valve guide disclosed in U.S. Pat. No. 2,222,457 to Scheibe includes two ends and a mid-portion. The mid portion being of a smaller diameter than the two end portions. The first end being smaller than the second end, so that the guide may be inserted from upper surface, or exterior of the head, towards the runner. Unfortunately, however, the insertion of the guide from the exterior of the head towards the runners presents the disadvantage that retention and sealing of the insert is made difficult by the fact gases for combustion tend to exert a resultant force in the direction in which the insert may be removed. This may lead to loosening and leakage of fluids, and even complete separation of the insert from the head.
A review of known devices reveals that there remains a need for a valve guide insert which can be used as a retrofit for existing heads to reduce the size of the valve guide boss and its effects on the flow through the runner or flow duct in the head.
Still further, there remains a need for a valve guide insert that can be progressively tightened against the head.
Importantly, known devices have not addressed the need for a a simple valve guide system that allows the control of oil delivery to the valve stem, and thus reduce the seepage of oil between the stem and the guide with wear of the guide.